Spectral Noise Levels and Roughness Severity Ratings for Normal and Simulated Rough Vowels Produced by Adult Females

Twenty normal-speaking adult females sustained seven-second productions of the vowels /u/, /i/, /Λ/, /a/, and /æ/ first normally and then with simulated vocal roughness at one intensity. Recordings of the vowels were rated for roughness on a five-point equal-appearing intervals scale by 11 trained judges. Each production was also analyzed to produce a 3-Hz bandwidth frequency-by-amplitude acoustic spectrum in which the level of inharmonic, i.e., noise, components was measured in dB SPL. Noise levels, averaged over selected frequency ranges from 100 to 8000 Hz, for each vowel production correlated highly with the median roughness ratings for the productions. High (≥0.97) and significant multiple correlation coefficients were obtained between each vowel’s 100-Hz section noise levels from 100 to 2600 Hz and its median roughness rating.